Introduction

Species of Pterygioteuthisare probably the smallest of all oceanic squids (Oegopsida). P. microlampas, for example, has a maximum size of 23 mm ML and short arms. One of the most distinctive features of the genus is the presence of a photophore on each eye that has a lid that can open and close over the organ. This photophore can produce a brilliant flash. The lid, presumably, allows a sudden beginning and end to the flash and, when closed, conceals the reflector that lies behind the photogenic tissue. Concealment is important as the reflector otherwise could reveal the squids presence in dark waters to predators that use luminescent search lights. A second pair of flashing photophores that lacks lids is located at the base of the gills. These latter organs are much larger than their counterparts in Pyroteuthis; the size difference is present in paralarvae and is helpful in distinguishing paralarvae of the two genera (Young, et al., 1992).

Members of the genus also have a distinctive hectocotylized arm that contains a peculiar toothed plate and large swollen regions containing folded, glandular tubes of unknown function (Chun, 1910).

Brief diagnosis:

A pyroteuthid ...

with suckers but without hooks on tentacular club.

with less than eight hooks on each arm.

Characteristics

Arms

Arm hooks in one or two series depending on species.

Less than 8 hooks/arm.

Female arms IV generally lack hooks with a maximum two hooks present on right arm IV in male P. giardi and P. hoylei.

Comments

Of the four species of Pterygioteuthis, 2 species groups are present based on similar morphological characters: P. giardi group (containing P. giardi and P. hoylei) and a P. gemmata group (containing P. gemmata and P. microlampas).

Discussion of Phylogenetic Relationships

The first in-depth cladistic analysis of Pterygioteuthis was based on 24 morphological characters (Lindgren, 2010) yielded two distinct clades: a P. gemmata group and a P. giardi group. Monophyly for Pterygioteuthis and Pyroteuthisas well as the family received high degrees of support.

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Figure. A phylogenetic topology of Pterygioteuthis based on 24 morphological character (Lindgren, 2010). Numbers in italics above nodes represent characters found in a specific clade (see Lindgren, 2010 for a description of characters and states). Numbers in bold below nodes represent jackknife suport values.

Behavior

P. microlampas and P. giardi have been observed to produce a variety of different bioluminescent flashes with their lidded-ocular and branchial photophores. The latter photophores can be rotated to point the flash in different directions. These two pairs of photophores can flash for varying durations and in various combinations suggesting that flashing behavior which, presumably, deters predators is complex (Young, et al., 1982). P. giardi has also been shown to counterilluminate in the laboratory (Young, et al., 1980).

Distribution

Species of Pterygioteuthisare found throughout the tropical and temperate regions of the world's oceans but are virtually absent from the Mediterranean Sea. This map shows the general localities (white circles) where species belonging to this genus have been captured. Localities where pyroteuthids, other than Pterygioteuthis, have been captured are indicated by orange crosses. Only one record per locality is included (records listed here).

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Members of Pterygioteuthis have a very interesting distribution pattern in the eastern Tropical Pacific.

Each ToL branch page provides a synopsis of the characteristics of
a group of organisms representing a branch of the Tree of Life. The
major distinction between a branch and a leaf of
the Tree of Life is that each branch can be further subdivided into
descendent branches, that is, subgroups representing distinct genetic
lineages.